Incheon, Republic of Korea · 8 October 2018
The Intergovernmental Panel on Climate Change (IPCC) released its Special Report on Global Warming of 1.5°C (SR15) on 8 October 2018, following a week-long approval session in Incheon, Republic of Korea. The report, prepared in response to an invitation from the United Nations Framework Convention on Climate Change (UNFCCC) following the 2015 Paris Agreement, provided the most comprehensive scientific assessment to date of the impacts of 1.5°C of global warming and the emissions pathways required to limit it.
The report synthesized over 6,000 scientific references and was produced by 91 authors and review editors from 44 countries, drawing on contributions from hundreds of expert reviewers. It represented the IPCC's first dedicated assessment of the 1.5°C target, which the Paris Agreement had established as an aspirational goal alongside the more widely discussed 2°C limit.
The Central Finding: 1.5°C vs. 2°C
The report's most consequential conclusion was that the difference between 1.5°C and 2°C of warming is not marginal — it is the difference between manageable and catastrophic impacts for many ecosystems and human communities. Every additional fraction of a degree matters.
At the time of the report, human activities had already caused approximately 1.0°C of global warming above pre-industrial levels. If the current rate of warming continued, the 1.5°C threshold would likely be reached between 2030 and 2052.
The report detailed specific impacts that would be substantially worse at 2°C compared to 1.5°C:
| Impact Area | At 1.5°C | At 2°C |
|---|---|---|
| Coral reefs | 70–90% decline | >99% decline |
| Sea-level rise by 2100 | 0.26–0.77m | 0.10m higher on average |
| Arctic sea ice-free summers | Once per 100 years | At least once per 10 years |
| Species losing >50% of range | 6% of insects, 8% of vertebrates, 18% of plants | 18% of insects, 16% of vertebrates, 16% of plants |
| Global population exposed to severe heatwaves | 2.0x increase | 2.7x increase |
The Scale of Transformation Required
The IPCC was unambiguous about the magnitude of change needed. Limiting warming to 1.5°C would require "rapid, far-reaching and unprecedented changes in all aspects of society" — language that drew significant attention and signaled a departure from the more measured tone of previous IPCC reports.
The report outlined four primary emissions reduction strategies:
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Energy systems transition: A major shift from fossil fuels to renewable energy sources, with renewables projected to supply 70–85% of electricity by 2050 in 1.5°C-compatible pathways.
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Energy efficiency: Deep improvements in energy efficiency across buildings, industry, and transport, reducing energy demand by approximately 15% by 2050 compared to 2010 levels.
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Land use changes: Afforestation, reforestation, and shifts in agricultural practices to reduce emissions and enhance carbon sinks.
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Carbon dioxide removal (CDR): Because historical emissions have already committed the planet to some level of warming, the report acknowledged that limiting warming to 1.5°C might involve a temporary "overshoot" of the threshold, requiring CDR techniques to bring temperatures back down.
The Overshoot Question
One of the report's most technically complex findings concerned the possibility of "overshoot" — temporarily exceeding 1.5°C before returning below it through large-scale carbon removal. The IPCC found that several 1.5°C-compatible pathways involve overshoot, and that the higher the overshoot, the greater the reliance on CDR technologies that are currently unproven at scale.
This finding generated significant debate. Some scientists and policymakers argued that overshoot pathways create a moral hazard — the assumption that future technology will solve the problem reduces the urgency of near-term emissions cuts. Others noted that overshoot may be unavoidable given the emissions already locked in, and that planning for it is simply realistic risk management.
Reception and Impact
The report's release was met with intense global attention. The stark framing — that the world had approximately 12 years to implement transformative change — became one of the most widely cited statistics in climate discourse. The report was referenced in subsequent UN climate negotiations, national climate plans, and the European Green Deal.
The report also faced criticism from some quarters. A few scientists argued that the 1.5°C target was no longer achievable given the trajectory of global emissions, and that focusing on it could divert attention from the more realistic task of limiting warming to well below 2°C. Others noted that the reliance on CDR technologies in many pathways represented an untested bet on future technological capacity.
The IPCC Process
The IPCC does not conduct original research. It assesses the scientific literature, operating through three working groups: Working Group I (physical science basis), Working Group II (impacts, adaptation, and vulnerability), and Working Group III (mitigation). SR15 was a cross-working group product, integrating physical science, impact analysis, and mitigation pathways into a single assessment.
The report underwent two rounds of expert review, with over 2,000 reviewer comments addressed. The Summary for Policymakers (SPM) — the most widely read section — was approved line-by-line by government representatives during the Incheon session, a process that ensures political buy-in but can also dilute scientific language through negotiation.
Image: IPCC Special Report on Global Warming of 1.5°C. Credit: IPCC
Sources
- IPCC Special Report on Global Warming of 1.5°C (8 October 2018):
- IPCC press release:
- Summary for Policymakers (PDF):
- Climate Central analysis:
- C40 Knowledge Hub:
FIRAT Editorial Board
Institutional Research Desk · Foresight Institute of Research and Translation
The collective editorial and research translation board of FIRAT, synthesising peer-reviewed evidence, policy briefs, and division milestones across our seven foundational research pillars.
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